Adrenolukodystrophy (ALD) is an X-linked disorder which affects the white matter of the nervous system and the adrenal cortex. It is a progressive and often fatal disease. We have shown that hemizygotes with ALD have increased levels of saturated very long chain fatty acids in cultured skin fibroblasts and in their plasma. These fatty acids include hexacosanoic (C26) and pentacosanoic (C25) acid. Increases have also been demonstrated in most ALD obligate heterozygotes and in the cultured amniotic fluid cells from a fetus who was later shown to be an ALD carrier. We plan to continue these studies so that we can construct risk criteria for women who are concerned whether or not they are carriers, and to determine whether we can identify prenatally the ALD hemizygote.